Optical systems in applications from display lighting and projection systems to automotive or medical lighting are subject to a virtual prototyping during a first design phase. Further, respective design tools also allow a continuous improvement during a product cycle. The tools used therein apply a ray tracing technique, with which a propagation of individual light rays through a virtual optical system can be calculated. A virtual model of the optical system can for example be imported from a lens design or CAD program or be generated by the ray tracing program itself.
The data on the light source is provided as a set of rays, wherein each ray is characterized by a starting point, a direction, and a light power, which is typically weighted by a spectral sensitivity of the human eye and indicated as luminous flux. In addition, there may be information on color for each ray, for instance in the form of a wavelength or tristimulus values. Then, the rays are traced through the optical system, and the transmission properties of the system can subsequently be derived by summing up the luminous flux of rays passing through to an exit aperture. Maximizing the transmission requires a plurality of such tracing steps, each performed with a slightly modified virtual model. Thus, an optimization is time-consuming and costly.
One object of the invention is to provide an improved method of modeling an illumination device.